Unrestricted submarine warfare is a type of naval warfare in which submarines sink merchant ships without warning, as opposed to attacks per prize rules. While providing the submarine with strongly increased lethality and greater chances of survival against its hunters, it was also considered by many as a substantial breach of the rules of war, especially when employed against neutral country vessels in a war zone.

There have been four major campaigns of unrestricted submarine warfare:

1. The First Battle of the Atlantic during World War I, waged intermittently by Germany between 1915 and 1918 against Britain and her allies. This warfare was also ostensibly the casus belli for the United States and Brazil's entry into the war in 1917.
2. The Second Battle of the Atlantic during World War II between 1939 and 1945, waged by Italy (from 1940 to 1943) and Germany mainly, against Britain and her allies.
3. The Naval War on Eastern Front, also during World War II between 1941 and 1945, waged by Germany and the USSR against each other, primarily on the Baltic Sea, specially from 1942.
4. The Pacific War during World War II, also between 1941 and 1945, waged by the United States against Japan.

All the four cases centered around attempts to navally blockade countries, especially those heavily dependent on merchant shipping to supply their war industries and feed their populations (like Britain and Japan), even though the countries waging the unrestricted submarine warfare were unable to institute a typical naval blockade.

History

Before WWI

In 1912, British Admiral Sir John "Jackie" Fisher, by then a retired First Sea Lord, presented a paper to the Cabinet. He developed the argument that submarines would find adherence to Prize Rules impossible, for practical reasons: a submarine could not capture a merchant ship, for it would have no spare manpower to deliver the prize to a neutral port, neither could it take survivors or prisoners, for lack of space. "...there is nothing a submarine can do except sink her capture." If a merchant ship were armed, as was permitted by a conference in London in 1912, then a submarine would be under even more pressure to destroy it. He asked: "What if the Germans were to use submarines against commerce without restriction?"

This last comment was thought to be unsupportable. Winston Churchill, then [[Admiralty|First Lord of The Admiralty]] and political head of the Navy, supported by senior naval opinion, said it was inconceivable that "...this would ever be done by a civilised power."

It was Fisher who was proved correct, though—as will be shown in the following section—the Germans themselves did not plan for this kind of warfare and went in practice through the stages which Fisher had predicted.

World War I

The evidence suggests that Imperial Germany had not started World War I with an appreciation of the impact on commerce and supply that submarines could have. They had fewer than 30 operational boats, all with small torpedo capacities. At first, merchant ships would be stopped, occupants safely evacuated and then the vessel sunk, usually by gunfire, all following Cruiser Rules. This relatively dangerous, time-consuming process placed the German submarine—U-boat—at risk from Q-ships, defensive patrols and other anti-submarine measures adopted by the British admiralty.

Germany had practical strategic problems. War-weariness affected the German home situation. The best chance of achieving an early advantageous peace with Britain was considered to be the stifling of its trade and imports. The gamble that was taken was that unrestricted submarine warfare would critically damage Britain before an incensed United States could make a practical impact. Even before the entry of the United States into the war, the US had already effectively been on the side of Britain, trading heavily with the United Kingdom, while the UK in turn prevented all attempts at US-German trade via a classical surface ship naval blockade, only ineffectually circumvented by German merchant submarines like the Deutschland. Thus, commercial interests were already in favour of a US that was increasingly assertive in its own strength and its right to trade with whatever nation it desired to, technically neutral or not.

While the success of the submarines was no small blow to British supply lines, the gamble ultimately failed when it drew the United States into the war, and when the introduction of the convoy system cut shipping losses heavily again.

Despite unrestricted warfare in later years, the majority of submarine-caused shipping losses sustained by the Allies were via 'restricted' (Prize Regulations) warfare.

World War II

London Rules on naval warfare

The submarine sinking of merchant ships without warning is in violation of the 1930 First London Naval Treaty, which specifies that "...except in the case of persistent refusal to stop on being duly summoned, or of active resistance to visit or search, a warship, whether surface vessel or submarine, may not sink or render incapable of navigation a merchant vessel without having first placed passengers, crew and ship's papers in a place of safety. For this purpose the ship's boats are not regarded as a place of safety..."

However, the London Rules were obsolete before they were signed (though the Kriegsmarine based its Prize Rules on them). The use of disguised guns on auxiliary cruisers increased the risk inherent in stop-and-search rules, but the primary danger came from the wide-spread adoption of radio, which meant that a merchant could call for help as soon as a submarine appeared, even before it could issue its demands. Coupled with the rapidly-growing speed, range, and destructive power of combat aircraft, this technology ensured that complying with these rules would be suicide for any submarine.

Germany in the Atlantic

For the first few weeks of World War II, the German Navy attempted to honour Nazi Germany's treaty obligations, but that attempt was in trouble almost immediately following the sinking of SS Athenia by U 30, and it was abandoned at the end of November or the beginning of December 1939 with the issuing of War Order No. 154.

United States in the Pacific

The United States, from the first day it entered the Pacific War against the Japanese Empire, decided that unrestricted submarine warfare was to be carried out in the Pacific Ocean.

Post-WWII concept

Since the introduction of long-range anti-ship missiles after World War II, which are able to destroy a ship from beyond the horizon, the London Rules are universally regarded as entirely void. It is indicative that despite the rules being used in the indictment of Admiral Karl Dönitz, and although he was found guilty of breaching the 1936 Naval Protocol, his sentence was not assessed (no penalty was issued) on the ground of his breaches of the international law of submarine warfare at the Nuremberg Trials because evidence was presented to the court that both the Royal Navy and the United States Navy had issued similar orders.

Natalino Ronzitti pointed out that due to the advent of supersonic aircraft and missiles, that at times of war fleets of warships can justifiably have a moving cordon sanitaire under which shipping or aircraft within the cordon can be attacked without warning. He also states that The Royal Navy had such a zone around their fleet during the 1982 Falkland War and that as this action was in the relatively empty South Atlantic it did not raise the diplomatic problems that such an action might cause in a busy sea such as the Mediterranean. Ronzitti states that D. P O'Connell considers that such a cordon sanitaire in restricted shipping lanes, in the context of anti-submarine warfare, and found them to be lawful providing they were properly advertised.

Ronzitti was also of the opinion that during the 1982 Falkland War although the static "Maritime Exclusion Zone" the British issued around the Falkland Islands that excluded Argentinian shipping from within 200 miles of the islands was legal, but the issuing of the static "Total Exclusion Zone" (TEZ), if based on the Dönitz's Nuremberg Trial was not, because it excluded neutral as well as Argentinian shipping. The 1982 TEZ did not raise much of a diplomatic protest, but Ronzitti points out that when Saddam Hussein declared a similar 50 mile zone around Kharg Island it was condemned in three United Nations Security Council Resolutions (552, 582, and 598). However Ronzitti also pointed out though that some authors have suggested that if one borrows from the laws and customs of land, then attacks on neutral shipping carrying supplies which could aid an enemy's war effort (even if only economically) could be attacked, and that this is an area of the laws of war which are still in need of clarification.

See also

• Submarine warfare
• Intensified submarine warfare

• Defensively Equipped Merchant Ships
• Commerce raiding
• Tonnage war
• Arabic pledge
• Sussex pledge
• War Order No. 154
• Laconia incident
• Laconia Order

Notes

References

• Ronzitti, Natalino (1988). The Law of naval warfare: a collection of agreements and documents with commentaries, Martinus Nijhoff Publishers, ISBN 9024736528, 9789024736522
• Willmott, H. P. (2003). First World War - Dorling Kindersley